Mid'dorsal scale count over 287; fifth mid-dorsal scale much wider than 

 sixth; Utah 



Leptotyphlops humilis utahensis Tanner Utah Blind Snake 



11. With most or all of the large plates on the lower surface of the tail 



single; mostly poisonous snakes 12. 



With most of the large plates on the lower surface of the tail divided 



into two (sometimes with a few single plates) ; few poisonous and 



many harmless snakes 49. 



12. With a deep pit between the eye and the nostril; pupil of eye vertical; 



with a pair of hollow poison fangs, which are folded against the roof 



of the mouth when not in use; Family Crotalidae Pit' vipers 13. 



No pit between the eye and the nostril; pupil vertical or round; no poison 



fangs 44. 



13. No rattles on tail 14. 

 With rattles on the end of the tail 19. 



14. No loreal; with one of the upper labials reaching up to the eye 15. 

 With loreal; with two or three small scales between the eye and the 



upper labials 16. 



15. End of snout dark; contrast between cross bands and ground color more 



evident in adult than in young specimens; 111. to Ala. and Texas 

 Agkjstrodon p^scivorus leucostoma (Troost) 

 Western Water Moccasin, Cottonmouth 

 End of snout light, with a vertical dark bar on each side of rostral plate; 

 contrast between cross bands and ground color more evident in young 

 than in adult specimens; Va. to Ala. and Fla. 

 ••.<"( Agkistrodon piscivorus piscivorus (Lacepede) 



Eastern Water Moccasin, Cottonmouth 



16. Dorsal dark cross bands deeply hour-glass shaped, and not confluent with 



dark belly markings (See note at end of chapter) 17. 



Dorsal dark cross bands scarcely hour-glass shaped, and confluent with 



dark belly markings 18. 



17. Narrowed area of dorsal bands about three to five scales wide, never ab' 



sent; color rather dark; Miss, to Ala. and Neb. 

 Agkjstrodon mo\eson mo\eson (Daudin) 

 (Agkjstrodon mo\asen Beauvois) 

 (Ayicistrodon contortrix (Linn.) ) 



Northern Copperhead, Highland Moccasin, Chunkhead 

 Narrowed area of dorsal bands less than three scales wide or sometimes 

 entirely absent, so that some of the cross bands are usually broken on 

 the mid-dorsal line; color rather pale; Texas to 111. and southern At- 

 lantic states, except Florida 



Ag\istrodon mo\eson austrinus Gloyd and Conant 

 Southern Copperhead 



18. Cross bands broad and fairly regular, blending into color on sides of 



belly; Kansas to Texas 



Agkjstrodon mo\eson laticinctus Gloyd and Conant 

 Western Copperhead 



392 



